1. Field of the Invention
The invention relates to fiber optic communication, and more particularly, to a multiple-channel clock and data recovery scheme for re-timing fiber optic data input streams into a synchronous state.
2. Description of Related Art
With the advent of parallel ribbon fiber cable and optical component array integration, high-speed optical data communication links are becoming increasingly practical and desirable. It is a challenge in achieving low-cost parallel modules for formatting fiber optic data, however, to incorporate a data receiver that performs clock and data recovery on multiple data input channels simultaneously. A typical data communications receiver for a single-channel input system requires a clock recovery circuit to extract timing information from an incoming data bit stream.
The recovery clock provides synchronous sampling off of the input data bits.
Carrying this approach to a multi-channel input system, however, induces error into the system. The application of the typical single-channel approach to a multi-channel input system typically requires integrating multiple clocks, e.g. one clock per channel. However, integrating one clock per channel results in multiple clocks that are competing on a single integrated circuit. The multiple clocks each tend to accumulate jitter due to the cross-coupling of the associated relatively high-power signals.
A need exists, therefore, for a multiple-channel clock and data recovery scheme that is capable of outputting a single clock signal to re-time all of the multiple channel data and that is thereby able to reduce the jitter and channel crosstalk that can occur with multiple clocks.